1. Field of the Invention
The invention relates to the field of air handling and more particularly to externally attached cabinets and their apparatus for filtering, heating, cooling and dehumidifying air within equipment enclosures.
2. Background Information
Control of the climate or environment within equipment enclosures is known and is commonly accomplished with an air conditioning system. The air conditioning system is either part of the building support equipment or it is attached to the exterior of the electrical equipment enclosure to provide conditioned air to the enclosure. In the field, most air conditioning systems recirculate the air within the equipment enclosure and do not allow significant mixing of outside air with inside air. In temperate regions, the air conditioning system typically removes humidity from the recirculated air at the same time it cools the air within the electrical equipment enclosure. The systems may also include filters to remove particulate in the recirculated air. In cold areas, the air conditioning system may alternatively heat the recirculated air and/or add moisture. When the systems heat the air, heating is normally accomplished with a heat pump, which is able to perform both heating and cooling functions.
An objective when controlling the recirculated air environment within the electrical equipment enclosure is to create and maintain an environment inside the enclosure that is different than the environment outside the enclosure. This objective is economically accomplished by recirculating the air and by reducing or eliminating the mixing of inside and outside air. Seals between inside and outside help eliminate mixing.
U.S. Pat. No. 5,657,641, issued to Cunningham et al. (the '641 patent), the disclosure of which is hereby incorporated by reference, discloses an apparatus to create and maintain an environment within an equipment enclosure. As described in the '641 patent, it is known to attach a cabinet to the exterior of an equipment enclosure, the cabinet containing heating, cooling and/or filtering equipment. The heating, cooling and/or filtering equipment typically includes blowers, a compressor, a condenser coil and an evaporator coil, and ducting to direct air flows through the condenser coil and evaporator coil to heat and cool the respective air streams. It is also common for condensate to form on the evaporator coil, which may drip from the evaporator coil into some form of collection pan. Depending on the application, the condensate is either drained from the cabinet or evaporated within the cabinet.
In most applications, introduction of condensate from the air conditioning cabinet into the electrical equipment enclosure is damaging and potentially dangerous. For many of these applications, condensate discharge either inside the cabinet or outside the cabinet is unacceptable. Thus, it is appropriate and advantageous to ensure that all condensate is evaporated within the cabinet during operation. Therefore, configurations that minimize or avoid the possibility of condensate entering into the electrical equipment enclosure are appropriate and advantageous.
When the cabinet is mounted on the exterior of the equipment enclosure it is subject to any local weather effects, such as rain, sleet, snow and wind. It is therefor necessary for the cabinet and enclosure to have suitable connections and seals. When securely connected to the enclosure, the cabinet and enclosure should not be separated in high winds, and precipitation should not enter either the cabinet or enclosure. Though it is common for the air conditioning cabinet to be mounted on the side of the electrical equipment enclosure, it is also possible to mount the cabinet on the top of the enclosure. Depending on the mounting location, the internal orientation of air conditioning equipment in the cabinet changes.
When an air conditioning cabinet is externally mounted to the equipment enclosure, the construction quality of the cabinet is visible. The connection of the air conditioning cabinet to the equipment enclosure is also visible. Previously known mounting configurations include an external flange arrangement such as disclosed in the '641 patent. In the flange arrangement disclosed in the '641 patent, screws or bolts attaching the cabinet to the enclosure are exposed to view and the environment. This exposed flange mounting configuration can be less attractive. Additionally, screws or bolts may corrode unless they are corrosion resistant. Mounting configurations that provide a pleasing and uncluttered appearance, are advantageous.
Apparatus and methods for air handling that address these and other problems are needed.